1. Field of the Invention
The present invention relates to an apparatus for measuring a shape of an object surface, for example a shape of a corneal surface in an eyeball.
2. Related Background Art
A conventional measuring apparatus for measuring a shape of a corneal surface in an eyeball as an object surface are normally arranged, for example as disclosed in Japanese Laid-open Patent Application No. 57-197404, such that light from a projection optical system projecting an index onto the surface of the cornea, is guided through an objective lens and split into an observation path and a measurement path by an optical splitter such as a beam splitter. There are known some of such measuring apparatus in which the reflected light from the corneal surface is split by the optical splitter into the observation path and the measurement path and in which a photoelectric converter for measurement is used also for observation for positioning of the eyeball as the object.
However, if a measuring apparatus is constructed as described above, i.e., such that the reflected light from the corneal surface is split by the optical splitter into the observation path and the measurement path, the scale of apparatus become large and the structure complex. Further, Japanese Laid-open Patent Application No. 57-197404 discloses another structure in which an eyeball as object is observed through an eyepiece and is guided to a predetermined position, which is complicated in operation.
A further drawback exists in the conventional arrangement in which the optical path is split into two and the photoelectric converter for measurement is also used for observation. In such arrangement, an optical system for measurement is constructed in the same manner as an optical system for observation. Thus, if a corneal image of an eyeball is formed on the photoelectric converter during observation at a magnification suitable for measurement, the magnification will be too high for observation, which limits the observation area to only a part of the eyeball. Therefore positioning of the eyeball is very difficult.